My invention deals generally with apparatus for writing or reading information on disklike record media such as flexible magnetic disks, and more particularly with such data transfer apparatus of the class having a drive pin resiliently supported in an eccentric position on an turntable, the drive pin being engageable in an eccentric opening in the record medium for imparting rotation thereto. Still more particularly, my invention pertains to a resilient support mechanism for the drive pin of such data transfer apparatus.
A flexible magnetic disk having an eccentric slot to be engaged by a drive pin, and a disk drive for use therewith, are both described and claimed in U.S. Pat. No. 4,445,157 to Takahashi. The magnetic disk proposed by this patent has a diameter of 3.5 inches (86 millimeters) and is rotatably housed in a generally flat, boxlike envelope of relatively rigid plastic material to make up a disk cassette. The magnetic disk has a rigid hub of magnetic material attached centrally thereto. The hub has defined therein a central opening of square shape and an eccentric opening or slot of rectangular shape. When positioned in the associated disk drive, the magnetic disk has its central hub placed on a turntable of much smaller diameter than that of the disk. The turntable has a permanent magnet mounted thereon for attracting the disk hub. Extending from the central position on the turntable is a drive spindle engageable in the central opening in the disk hub for centering the disk. A drive pin is disposed eccentrically on the turntable for driving engagement in the eccentric slot in the drive hub, imparting the rotation of the turntable to the magnetic disk.
The drive pin must be elastically supported for displacement relative to the turntable in a direction parallel to the axis of the drive spindle, so as to spring into engagement in the eccentric slot in the disk hub following the commencement of the rotation of the turntable.
I know two different types of leaf springs that have been herefore suggested and used for resiliently supporting the drive pin on the turntable. One of these, disclosed in the Takahashi patent, is supported at three different points. The other type of drive pin support spring is cantilevered, being supported at one point only or substantially at one point, as taught by Japanese Laid Open patent application No. 60-254457. The latter type is finding a greater acceptance in the disk drive manufacturing industry by reasons of the simplicity of construction and ease of assemblage.
The cantilevered drive pin support spring according to the noted Japanese patent application may be described as generally U-shaped, bored at one extremity to fit over the drive spindle and carrying the drive pin on the other extremity. I object to this prior art spring because the drive pin tends to elastically slant in the direction of rotation of the magnetic disk, to such an extent as to give rise to an angular displacement of the disk with respect to the turntable. The drive pin is received in the eccentric slot in the disk hub with very substantial clearance. Consequently, as in the event of abrupt changes in the head-loading pressure on the magnetic disk as a result of vibrations or shocks exerted on the disk drive, the angle of the drive pin with respect to the plane of the magnetic disk may change, possibly resulting in instantaneous speed variations of the disk.
A solution to this problem is found in Japanese Laid Open Utility Model application No. 60-163546, which teaches the provision of a fixed abutment on the turntable for limiting the slanting of the drive pin in a direction opposite to the rotational direction of the magnetic disk. This solution is unsatisfactory, however, because the leaf spring supporting the drive pin permits its slanting away from the abutment, that is in the rotational direction of the magnetic disk.